Failure rates of metal-on-metal hip resurfacings: analysis of data from the National Joint Registry for England and Wales.

BACKGROUND: Implant survival after conventional total hip replacement (THR) is often poor in younger patients, so alternatives such as hip resurfacing, with various sizes to fit over the femoral head, have been explored. We assessed the survival of different sizes of metal-on-metal resurfacing in men and women, and compared this survival with those for conventional stemmed THRs.

METHODS: We analysed the National Joint Registry for England and Wales (NJR) for primary THRs undertaken between 2003 and 2011. Our analysis involved multivariable flexible parametric survival models to estimate the covariate-adjusted cumulative incidence of revision adjusting for the competing risk of death.

FINDINGS: The registry included 434,560 primary THRs, of which 31,932 were resurfacings. In women, resurfacing resulted in worse implant survival than did conventional THR irrespective of head size. Predicted 5-year revision rates in 55-year-old women were 8·3% (95% CI 7·2-9·7) with a 42 mm resurfacing head, 6·1% (5·3-7·0) with a 46 mm resurfacing head, and 1·5% (0·8-2·6) with a 28 mm cemented metal-on-polyethylene stemmed THR. In men with smaller femoral heads, resurfacing resulted in poor implant survival. Predicted 5-year revision rates in 55-year-old men were 4·1% (3·3-4·9) with a 46 mm resurfacing head, 2·6% (2·2-3·1) with a 54 mm resurfacing head, and 1·9% (1·5-2·4) with a 28 mm cemented metal-on-polyethylene stemmed THR. Of male resurfacing patients, only 23% (5085 of 22076) had head sizes of 54 mm or above.

INTERPRETATION: Hip resurfacing only resulted in similar implant survivorship to other surgical options in men with large femoral heads, and inferior implant survivorship in other patients, particularly women. We recommend that resurfacing is not undertaken in women and that preoperative measurement is used to assess suitability in men. Before further new implant technology is introduced we need to learn the lessons from resurfacing and metal-on-metal bearings.

FUNDING: National Joint Registry for England and Wales.